The present invention is directed to a needle safety shield for a syringe having a barrel, a needle and a plunger rod. More, particularly, the present invention is directed to a needle safety shield having a position biased actuation assembly.
Needlestick injuries are a well known occupational hazard for healthcare workers. Unintended needlesticks have the potential for transmitting blood-borne viruses such as hepatitis B and C and the human immunodeficiency virus (HIV) to the recipient. After a needlestick injury, certain procedures must be followed to minimize the risk of infection for the recipient, such as laboratory blood tests and post-exposure prophylaxis started immediately after exposure to a pathogen, such as one of the aforementioned viruses, in order to prevent infection by the pathogen and the development of the associated disease.
Conventional safety devices intended to reduce the frequency of post-injection needlesticks typically have a sheath partially or completely surrounding the pharmaceutical syringe. The sheath may be held in a retracted position exposing the needle for aspiration and injection and may be automatically deployed around a needle afterwards.
One example of a common safety injection device for a syringe is disclosed in U.S. Pat. No. 7,678,086. The disclosed safety injection device has a support sheath secured to a syringe barrel. Prior to an injection, a needlestick protection sheath is held in a retracted position exposing the syringe needle by radially outwardly biased latches that rest on a shoulder of the interior wall of the support sheath. At the end of the injection, the head of the syringe piston dislodges the latches allowing a thrust spring to move the protection sheath to an extended position beyond the distal end of the needle, thereby preventing exposure of a healthcare worker to the needle tip. At least one known deficiency of the safety injection device is that a shock or vibration prior to assembly of the syringe may unexpectedly cause the latches to release and the protection sheath to move to the extended position.
Accordingly, there is a need in the art for a safety injection device having a protection sheath that can not be inadvertently activated.